package com.uchiha.nova.core.service;



import com.uchiha.nova.core.common.AbstractNovaProcessor;
import com.uchiha.nova.core.common.MultiSetMap;
import com.uchiha.nova.core.common.Sets;
import com.uchiha.nova.core.common.TypeHelper;

import javax.annotation.processing.Filer;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedOptions;
import javax.lang.model.element.*;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.ElementFilter;
import javax.lang.model.util.Elements;
import javax.lang.model.util.SimpleAnnotationValueVisitor8;
import javax.lang.model.util.Types;
import javax.tools.FileObject;
import javax.tools.StandardLocation;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.util.*;
import java.util.stream.Collectors;

/**
 * @author 周林静
 * @Date 2021-10-26 9:35
 * @Version 1.0
 */
@SupportedOptions("debug")
public class AutoServiceProcessor extends AbstractNovaProcessor {
    /**
     * spi 服务集合，key 接口 -> value 实现列表
     */
    private final MultiSetMap<String, String> providers = new MultiSetMap<>();
    private TypeHelper typeHelper;

    @Override
    public synchronized void init(ProcessingEnvironment env) {
        super.init(env);
        this.typeHelper = new TypeHelper(env);
    }

    @Override
    public Set<String> getSupportedAnnotationTypes() {
        return Sets.ofImmutableSet(AutoService.class.getName());
    }

    @Override
    protected boolean processImpl(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        if (roundEnv.processingOver()) {
            generateConfigFiles();
        } else {
            processAnnotations(annotations, roundEnv);
        }
        return true;
    }

    private void processAnnotations(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(AutoService.class);

        log(annotations.toString());
        log(elements.toString());

        for (Element e : elements) {
            TypeElement providerImplementer = (TypeElement) e;
            AnnotationMirror annotationMirror = getAnnotationMirror(e, AutoService.class);
            if (annotationMirror == null) {
                continue;
            }
            Set<TypeMirror> typeMirrors = getValueFieldOfClasses(annotationMirror);
            if (typeMirrors.isEmpty()) {
                error("No service interfaces provided for element!", e, annotationMirror);
                continue;
            }
            for (TypeMirror typeMirror : typeMirrors) {
                String providerInterfaceName = typeHelper.getType(typeMirror);
                Name providerImplementerName = providerImplementer.getQualifiedName();

                log("provider interface: " + providerInterfaceName);
                log("provider implementer: " + providerImplementerName);

                if (checkImplementer(providerImplementer, typeMirror)) {
                    providers.put(providerInterfaceName, typeHelper.getType(providerImplementer));
                } else {
                    String message = "ServiceProviders must implement their service provider interface. "
                            + providerImplementerName + " does not implement " + providerInterfaceName;
                    error(message, e, annotationMirror);
                }
            }
        }
    }

    private void generateConfigFiles() {
        Filer filer = processingEnv.getFiler();

        for (String providerInterface : providers.keySet()) {
            String resourceFile = "META-INF/services/" + providerInterface;
            log("Working on resource file: " + resourceFile);
            try {
                SortedSet<String> allServices = new TreeSet<>();
                try {
                    FileObject existingFile = filer.getResource(StandardLocation.CLASS_OUTPUT, "", resourceFile);
                    log("Looking for existing resource file at " + existingFile.toUri());
                    Set<String> oldServices = ServicesFiles.readServiceFile(existingFile.openInputStream());
                    log("Existing service entries: " + oldServices);
                    allServices.addAll(oldServices);
                } catch (IOException e) {
                    log("Resource file did not already exist.");
                }

                Set<String> newServices = new HashSet<>(providers.get(providerInterface));
                if (allServices.containsAll(newServices)) {
                    log("No new service entries being added.");
                    return;
                }

                allServices.addAll(newServices);
                log("New service file contents: " + allServices);
                FileObject fileObject = filer.createResource(StandardLocation.CLASS_OUTPUT, "", resourceFile);
                OutputStream out = fileObject.openOutputStream();
                ServicesFiles.writeServiceFile(allServices, out);
                out.close();
                log("Wrote to: " + fileObject.toUri());
            } catch (IOException e) {
                fatalError("Unable to create " + resourceFile + ", " + e);
                return;
            }
        }
    }

    /**
     * Verifies {@link java.util.spi.LocaleServiceProvider} constraints on the concrete provider class.
     * Note that these constraints are enforced at runtime via the ServiceLoader,
     * we're just checking them at compile time to be extra nice to our users.
     */
    private boolean checkImplementer(TypeElement providerImplementer, TypeMirror providerType) {
        // TODO: We're currently only enforcing the subtype relationship
        // constraint. It would be nice to enforce them all.
        Types types = processingEnv.getTypeUtils();

        return types.isSubtype(providerImplementer.asType(), providerType);
    }

    /**
     * 读取 AutoService 上的 value 值
     *
     * @param annotationMirror AnnotationMirror
     * @return value 集合
     */
    private Set<TypeMirror> getValueFieldOfClasses(AnnotationMirror annotationMirror) {
        return getAnnotationValue(annotationMirror, "value")
                .accept(new SimpleAnnotationValueVisitor8<Set<TypeMirror>, Void>() {
                    @Override
                    public Set<TypeMirror> visitType(TypeMirror typeMirror, Void v) {
                        Set<TypeMirror> declaredTypeSet = new HashSet<>(1);
                        declaredTypeSet.add(typeMirror);
                        return Collections.unmodifiableSet(declaredTypeSet);
                    }

                    @Override
                    public Set<TypeMirror> visitArray(
                            List<? extends AnnotationValue> values, Void v) {
                        return values
                                .stream()
                                .flatMap(value -> value.accept(this, null).stream())
                                .collect(Collectors.toSet());
                    }
                }, null);
    }

    /**
     * Returns a {@link ExecutableElement} and its associated {@link AnnotationValue} if such
     * an element was either declared in the usage represented by the provided
     * {@link AnnotationMirror}, or if such an element was defined with a default.
     *
     * @param annotationMirror AnnotationMirror
     * @param elementName      elementName
     * @return AnnotationValue map
     * @throws IllegalArgumentException if no element is defined with the given elementName.
     */
    public AnnotationValue getAnnotationValue(AnnotationMirror annotationMirror, String elementName) {
        Objects.requireNonNull(annotationMirror);
        Objects.requireNonNull(elementName);
        for (Map.Entry<ExecutableElement, AnnotationValue> entry : getAnnotationValuesWithDefaults(annotationMirror).entrySet()) {
            if (entry.getKey().getSimpleName().contentEquals(elementName)) {
                return entry.getValue();
            }
        }
        String name = typeHelper.getType(annotationMirror);
        throw new IllegalArgumentException(String.format("@%s does not define an element %s()", name, elementName));
    }

    /**
     * Returns the {@link AnnotationMirror}'s map of {@link AnnotationValue} indexed by {@link
     * ExecutableElement}, supplying default values from the annotation if the annotation property has
     * not been set. This is equivalent to {@link
     * Elements#getElementValuesWithDefaults(AnnotationMirror)} but can be called statically without
     * an {@link Elements} instance.
     *
     * <p>The iteration order of elements of the returned map will be the order in which the {@link
     * ExecutableElement}s are defined in {@code annotation}'s {@linkplain
     * AnnotationMirror#getAnnotationType() type}.
     *
     * @param annotation AnnotationMirror
     * @return AnnotationValue Map
     */
    public Map<ExecutableElement, AnnotationValue> getAnnotationValuesWithDefaults(AnnotationMirror annotation) {
        Map<ExecutableElement, AnnotationValue> values = new HashMap<>(32);
        Map<? extends ExecutableElement, ? extends AnnotationValue> declaredValues = annotation.getElementValues();
        for (ExecutableElement method : ElementFilter.methodsIn(annotation.getAnnotationType().asElement().getEnclosedElements())) {
            // Must iterate and put in this order, to ensure consistency in generated code.
            if (declaredValues.containsKey(method)) {
                values.put(method, declaredValues.get(method));
            } else if (method.getDefaultValue() != null) {
                values.put(method, method.getDefaultValue());
            } else {
                String name = typeHelper.getType(method);
                throw new IllegalStateException(
                        "Unset annotation value without default should never happen: " + name + '.' + method.getSimpleName() + "()");
            }
        }
        return Collections.unmodifiableMap(values);
    }

    public AnnotationMirror getAnnotationMirror(Element element, Class<? extends Annotation> annotationClass) {
        String annotationClassName = annotationClass.getCanonicalName();
        for (AnnotationMirror annotationMirror : element.getAnnotationMirrors()) {
            String name = typeHelper.getType(annotationMirror);
            if (name.contentEquals(annotationClassName)) {
                return annotationMirror;
            }
        }
        return null;
    }

}
